Oncologic and reproductive outcomes of cystectomy as a fertility-sparing treatment for early-stage epithelial ovarian cancer Abstract Background Fertility-sparing surgery (FSS) has mainly been chosen for young women with ovarian-confined/well-differentiated epithelial ovarian cancer (EOC). In general, FSS consists of at least conservation of contralateral ovary and the uterus with a staging surgery. However, information on the clinical outcome in women who underwent cystectomy as a fertility-preserving option is lacking. Methods After a central pathological review and search of the medical records from multiple institutions between 1987 and 2015, a total of eight early-stage EOC patients treated with cystectomy as FSS were retrospectively evaluated. Diagnosis and staging were based on International Federation of Gynecology and Obstetrics criteria (2014). Surgery consisted of uni- or bilateral cystectomy. The oncologic and reproductive outcomes were assessed. Results The median age was 29 years (range 26–38 years). The median follow-up time was 103.6 months (range 42.2–218.3 months). The stage was IA in 3, IC1 in 4, and IC3 in one patient. Five patients received adjuvant chemotherapy. After cystectomy, two patients experienced recurrence in the pelvic cavity and bilateral ovaries, respectively. The former patient died of the disease 42 months after cystectomy, and conversely, the latter one was rescued by subsequent radical surgery. Four full-term childbirths were observed in three patients. Conclusions Although oophorectomy is considered as an appropriate fertility-preserving operation, cystectomy may be an unavoidable option when it is the only surgical procedure available. It is desirable to verify the utility by accumulating larger numbers of patients through a future registry system.